The invention relates to a rotary mobile crane that is capable of handling very large loads, lifting the loads to very large heights, working in a confined area (being able to deposit loads directly at the base of the crane) while still having great range, and one that can be broken down for easy transport on all types of highways, on most without requiring the securement of special permits and the like. There are a large number of rotary mobile cranes in the prior art, such as those disclosed in U.S. Pat. Nos. 2,924,341, 3,045,837, and 3,190,457. While such cranes are generally useful, they are not readily adaptable for the ready lifting and moving of very large loads over a full range of movement as is the present invention.
The mobile rotary crane of the present invention comprises a mobile vehicular support, a crane base mounted on the vehicular support for rotation with respect thereto, and an assemblable main boom pivotally mounted to said crane base, and movable from a generally horizontal position, whereat it can be assembled and disassembled, to a generally vertical position, the normal operating position thereof. Great lifting power is obtainable with the crane by the provision of a jib boom pivotally mounted to the main boom on the load side thereof, a tower extending upwardly from the main boom and providing a support for cables and pulley arrangements for pivoting the jib boom with respect to the main boom, the tower being at least 1/3 the length of the jib boom, and counterweight mounted on the crane base on the side of the main boom opposite the load side thereof. Provision is made to prevent the jib boom from tipping over when the jib boom is in a substantially vertical position by providing a reeving assembly for the cable for pivoting the jib boom on the load side of the main boom. Means for movement of the main boom into vertical operating position, and for allowing booming out of the main boom during lifting (to increase the horizontal range of movement, and to preclude tipping over of the crane when being moved along the ground while assembled) comprise a pair of lever arms disposed at a substantially 90.degree. angle with respect to the main boom, cables extending around pulleys mounted on the free ends of the lever arms being attached at one end thereof to the free end of the main boom, and at the other end thereof to a drive assembly for allowing the cables to be pulled in and let out to thereby pivot the main boom about its horizontal pivot axis. Extra support may be provided for the main boom by spud booms disposed on either side of the main boom and attached along the horizontal pivot axis thereof, and by a strongback assembly including a pair of cables attached to the top of the tower and the cables for lifting the main boom, and passing over an extension of the main boom on the counterweight side thereof.
Ease of movement of the crane is provided, both with the main boom assembled for on-the-job movement, and for transport along the highway, by the mobile vehicular support. The vehicular support includes a pair of end sections and a center section, the center section mounting the crane base thereon. Each end section has mounted thereto a wheel train assembly, a plurality of axles associated with each wheel train assembly. At least some of the wheels of each wheel train are steerable, and at least some of the wheels of at least one of the wheel trains are powered. The wheel trains are mounted for pivotal movement with respect to the end sections both about a horizontal and a vertical axis to allow both for steering thereof and movement thereof on inclined ground. A plurality of rams extend between each of the wheel trains and their respective end sections to insure that the end sections remain horizontal at all times during vehicular movement despite the incline of the terrain on which the wheels of the wheel trains are moving. Outrigger means are provided with the center section of the vehicular support, extending from each side thereof, for stabilization of the crane during lifting therewith. Stabilizing rams are associated with both outrigger means and with the center section for lifting the wheels of the wheel trains slightly off the ground during operation of the crane, the stabilizing rams providing a solid base for supporting the crane during lifting. The crane base includes main beams and a cross-beam, the main boom being pivotally mounted to the main beams at the intersection thereof with the cross-beam. The cross-beam may be detached from the crane base, along with the main boom, for ease of transport on highways (the vehicular support being no wider than a normal highway lane, and the beams being spaced apart no more than the width of a normal highway lane), and the main beams may be removable from the crane base also, and the outrigger means pinned up in a vertical position for ease of transport with the vehicular support.
It is the primary object of the present invention to provide an improved rotary mobile crane that can lift heavy loads, has a full range of movement with minimal chance of tipping, and can be moved easily on site while assembled, or on the highways after disassembly. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.